Detection Through Layers of Protection

Detection Through Layers of Protection

According to the Center for Effective Government, there have been over 400 petrochemical accidents in the U.S. during the last two years since President Obama issued an executive order in August 2013 to help improve petrochemical safety policies. These 400 accidents include a disturbing number of serious explosions and fires at petrochemical plants and other industrial plants that use petrochemicals, where the best safety practices and equipment should be in place.

Combustible gas and fire safety is a challenging problem at petrochemical process and industrial facilities of all kinds throughout the world, but worse in many developing countries. The recent catastrophic incident at Tianjin, China, while its cause is officially unknown, is likely another example of lax petrochemical safety practices. There is hope, however, because the latest generation of gas and flame safety detection systems is smarter than ever and can provide a layered human sensory approach that is more comprehensive to protect people and facilities.

The Plant Protection Problem
Detecting combustible gas leaks and flames at petrochemical plants can be a real challenge under the best of conditions. There are large indoor and outdoor areas to protect with a congested array of complex equipment, connecting pipes and tanks. Gas leaks also vary in their behavior based on their density and other factors such as the ambient temperature and nearby air flow, including the wind in outdoor areas. The problem is that no matter how many fixed gas and flame detectors are installed a leak or flame can still go undetected if it doesn’t come into contact with a gas sensor or can’t be seen by a flame sensor (see above figure).

Storage tanks and the pipelines that connect them are an excellent example of the challenge that petrochemical process and plant engineers face every day. They are located outdoors and subject to windy conditions, which can blow leaking combustible gas away from traditional gas detectors, such as catalytic bead sensors. These traditional sensors essentially “smell” the gas through a petrochemical reaction and initiate an alarm signal to the plant control system warning of the problem.

The major sensing technologies employed in the detection of combustible gas leaks and flames at petrochemical plants are: catalytic bead, point infrared (IR), open path IR, ultrasonic and optical. They are all well-known technologies with more than a decade of proven performance in the field. All of them have their unique advantages depending on the application environment. All of them are individually susceptible to false alarms under certain conditions. No single method of gas and flame detection is foolproof.

Gas leaks and flames come from a variety of sources within the petrochemical and industrial plant environment, including leaking tanks, pipes, valves, pumps, etc. Avoiding false alarms is also important because they result in unnecessary process or plant shutdowns, slowing production and requiring time-consuming reviews, paperwork, and reporting. False alarms can over time provide employees with a false sense of security because they become complacent if alarms go off for no apparent reason and then just choose to ignore them. The trouble is that you can’t really determine by yourself the difference between a false alarm and a serious accident about to happen.

It’s a challenge for anyone to detect dangerous gas leaks and flames reliably using any single one of the conventional technologies. IR detectors, for example, can’t detect hydrogen gas because hydrogen doesn’t absorb IR energy. In another example, while a pressurized pipe gas leak can create an ultrasonic noise so can other pieces of equipment that can trigger ultrasonic detectors. Optical flame detectors can be fooled by reflections or heat rising off tanks and other shiny surfaces on hot days.

The Human Sensory Model
Given the many challenges that all the best sensing technologies face, it’s not surprising that a new strategy in gas and flame protection is emerging for petrochemical and other industrial plants. What if you combined all of the gas and flame detection technologies together and then layered them where they fit best in terms of their reliability in each unique plant layout?

Detection Through Layers of Protection

When you think about today’s gas and flame detection sensing technologies, they mimic the senses of the people who invented them. Catalytic bead detectors “sniff” gases for example, infrared and optical type sensors “see” gases and flames, and ultrasonic sensors hear “gases”. What if some of these detectors behaved more like people, reacting based on their intelligence and retained past memories? Layering sensor technologies throughout the plant where they fit best in terms of their reliability achieves a human sensory chain of plant defense against hazardous gases and flames (see above figure). Watch our new detection technologies video to get a better understanding of the human sensory approach.

Conclusions
Applying the concept of a human sensory model builds a chain of defense to protect petrochemical and other industrial plants. This model allows process and plant engineers to add layers of protection that increase overall system reliability.

When assessing the safety requirements at your plant, please don’t hesitate to contact us to discuss your specific application. If you have a particular problem, we have most likely seen it and solved it before. Let us help you take any guesswork out of safety.

Watch our new gas detection technologies video to get a better understanding of the human sensory approach.




Copyright 2015 General Monitors, Inc. All logos, brand and product names are registered trademarks of their perspective owners. All rights reserved. Questions or comments to etech@generalmonitors.com.




              

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